An enhanced dedicated channel (E-DCH) is used as a transport channel for user equipment in a Cell_FACH state. The E-DCH is used for common control channel (CCCH), dedicated control channel (DCCH), and/or dedicated traffic channel (DTCH) transmissions. One CCCH message can be sent at multiple transmission timing intervals (TTIs) so that re-ordering is needed. On the E-DCH channel temporarily granted to particular user equipment, the data packets are set to the network. There are control channels in the downlink direction used to control the granting of resources to the user equipment. The user equipment recognizes which control messages that are relevant by the E-DCH Radio Network Temporary Identifier (E-RNTI). The E-RNTI is allocated by a base station (or Node B) when the user equipment establishes an E-DCH, and is unique within a cell carrying the E-DCH. The E-RNTI may be included in a media access control (MAC) header when the user equipment accesses the E-DCH common channel. An E-DCH absolute grant channel (AGCH) with the E-RNTI is used for contention resolution. No contention resolution is performed for CCCH.
The E-RNTI allocated to the user equipment has to be unique within the cell among all of the user equipment that are using the E-DCH (i.e., the user equipment that are in the Cell_FACH state and the user equipment that are in the Cell_DCH state).
For the enhanced Cell_FACH in the uplink, MAC-i and MAC-is are used to support the E-DCH transmission in the Cell_FACH state. One MAC-is entity per user equipment is located in the serving radio network controller (RNC) for handling DCCH/DTCH transmissions in the Cell_FACH state for the E-DCH. The MAC-is for CCCH is located in the controlling RNC.
For the downlink, Cell_FACH users may also use a high-speed packet access (HSPA) channel. User equipment in the Cell_FACH state receive data packets on a HS-DSCH instead of on the FACH. A HS-DSCH is a channel used in the high-speed downlink packet access (HSDPA) universal mobile telecommunications system (UMTS) that sends packets on a downlink to user equipment. With enhanced Cell_FACH in the downlink, users in a Cell_FACH state are allocated a HS-DSCH Radio Network Transaction Identifier (H-RNTI). An H-RNTI is allocated by a controlling RNC (CRNC) when the user equipment establish a HS-DSCH channel, and is unique within a cell carrying the HS-DSCH.
As described above, the E-RNTI is allocated by the base station whereas the H-RNTI is allocated by the controlling RNC. Even if allocation of E-RNTI in the base station has the advantage that the same node allocates the E-RNTI to users in both the Cell_FACH state and Cell_DCH state, and thus guarantee uniqueness of E-RNTI in the cell, such arrangements have several disadvantages. For example, such arrangements do not remove (or release) unused E-RNTIs allocated to Cell_FACH user equipment when required. Furthermore, as different nodes allocate the H-RNTI and the E-RNTI, the relation between a dedicated H-RNTI (e.g., used for enhanced FACH) and the E-RNTI is unknown to the nodes supporting the user equipment using the E-DCH in the Cell_FACH state. The base station needs to know this relation for discontinuous reception (DRX) and other radio channel handling purpose.